Methods relying on retinal persistence to allow the reconstruction of motion are known from the prior art. The phenakistiscope is known for example, which uses a cardboard disk, pierced with slits, wherein a motion is decomposed into a series of still images, and a stick enabling it to be held while it is rotating. The zoetrope is also known, which consists of a drum pierced with slits on its upper half and sheltering in the interior, in its lower part, a strip of drawings decomposing a motion. When the drum is rotated and the interior is stared at fixedly through the slits, the drawings are animated. The praxinoscope is also known, the operation of which relies on the principle of the zoetrope, which comprises several mirrors around its central axis so as to view the illusion of motion.
Furthermore, methods are known, described in documents U.S. Pat. No. 5,901,484, U.S. Pat. No. 6,286,873 and US 2005/0183300, for creating illusions of motion. These methods utilize the principle of decomposition of motion allowing the reconstruction of a motion “in frames”. A support carries several fragmented images, corresponding for example to the decomposition of an object or of an animal in motion, and a carrier transparent film bearing a network of parallel lines having a given thickness and spacing between the lines is placed on the support. A relative motion between the fragmented images and the network of parallel lines makes it possible to create the illusion of a motion.
The superposition of two elements, by folding of an article, is also known. Application WO 2006/029744 describes in particular the superposition, by folding of a document, of two optical elements making it possible to obtain different optical effects according to the distance separating said optical elements. Moreover, application WO 02/17242 describes the superposition, by folding of an article, of a hologram and of a hidden information item so as to reveal said hidden information item. Finally, application US 2006/0290136 describes the superposition, by folding of a document, of a coded image and of an optical lens to decode said image.
A method for identifying a document, for example a banknote, is furthermore known from application WO 2005/106808, consisting in superimposing a region of the document on an image displayed on a screen, the image arising from a decoding system dispatched via a network.
Further, a security element is known from application WO 2006/018171 comprising authentication characteristics exhibiting a first appearance in transmitted light and a second appearance, different from the first, when the security element is placed on a particular background, for example a liquid crystal display (LCD).
Also known is application DE 10 2007 037576 which describes a banknote comprising an at least partially transparent window in which appears a first hidden information part, and a liquid crystal display displaying a second hidden information part. The superposition of the first and second hidden-information parts makes it possible to reveal a recognizable information item. The screen can also make it possible to successively display various hidden-information parts which make it possible to successively observe various recognizable items of information when the banknote is superimposed on the screen.